Conclusion
CPET confirmed the presence of DB in the patient based on the low resting value of ETCO2, the presence of a chaotic pattern of respiration during resting and exercise with the presence of tachypnoea (with very low ventilatory efficiency) in maximal exertion. Diagnosis of DB using CPET is one of the methods of DB diagnostics. Proper respiratory rehabilitation and psychological guidance resulted in the patient fixing the respiratory pattern and subsequently eliminating the primary cause of the examination - chronic fatigue. Patients with CFS/ME are a common paediatric problem. The current possibilities of diagnostics are enriched by the possibility of performing CPET, which can be a benefit in differential diagnostics as well as in confirming the diagnosis.